Field of the Invention
The present invention relates, in general, to a fuel cell that enables uniform air, hydrogen, and cooling water distributions over a stack channel, suppresses flooding, and manages faulty cells.
Description of the Related Art
Improvement of the performance of a fuel cell at a high current requires a smooth supply of air. Currently, in fuel cell systems, air supply is achieved through a high voltage air compressor. In this case, when rotational speed (revolutions per minute (RPM)) of the compressor is increased for the purpose of increasing a flow rate of air for high output power, power consumption spikes and an overall efficiency of a fuel cell system decreases.
Furthermore, since the output power of a fuel cell depends on the flow rate of air, maximum output power of a fuel cell is limited by the limited flow rate of air. Accordingly, there is an increasing demand for a technology which can improve efficiency of a fuel cell while reducing concentration loss in a high output power region by increasing the flow rate of air and by maintaining constant rotational speed of the air compressor.
In general, a fuel cell generates electricity through electrochemical reaction between oxygen from air and hydrogen as fuel, producing water as a byproduct. The water produced at an electrode advantageously serves to adjust RH (Relative Humidity) of a membrane but also negatively functions for transmission of air into a gas distribution layer (GDL) or the electrode, by blocking the pores in the gas distribution layer or the electrode. The water produced is often not appropriately removed and as such a surplus exists at the electrode and within a channel (or the GDL). This phenomenon is called flooding Flooding impedes transfer of air and hydrogen, leading to a dramatic plunge in the performance of specific cells in a low output power region. Flooding is a main factor of the overall performance of a fuel cell and its associated limitations. When the flooding occurs, a driver experiences performance decline of a vehicle or feels hesitation even in a low power state.
For a fuel cell vehicle, when the flooding occurs, the water is removed by promptly increasing the flow rate of air. However, the increased flow rate is likely to result in an increase in power consumption, wearing down of the membrane, and deterioration in the durability of the membrane which is attributable to drying of the membrane. Accordingly, preferably, the occurrence of flooding should be prevented in advance. One of key factors of flooding is non-uniform air supply rather than insufficiency of supplied air. Accordingly, it is necessary to maintain a constant flow rate of air during air supply in order to prevent local flooding.
The present invention serves to eliminate disadvantageous conditions for uniform air supply through the use of equipment and devices suitable for a manifold, and to improve performance and stability of a system through active controls.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.